Scientists Edited HIV Out of a Human Genome

Staff Writer

July 21, 2014 // 02:38 PM EST

Lymphocytes in the immune system. Image: Shutterstock

As a retrovirus, HIV literally writes itself into the genome of the people it infects, which in turn programs a person's cells to make more viruses and thus remain infected. But a new human genome-editing technique has eradicated the virus from a human cell for the first time, in what could eventually function as an entirely new HIV treatment.

So far, true cures and vaccines for HIV have remained elusive (except for a few rare cases involving bone marrow transplants, as has just happened in two patients), in no small part because the HIV virus infects a cell with its RNA, which causes infected cells to implement it into the person's own genetic code. That's where a new technique, developed by Kamel Khalili and Wenhui Hu of Temple University, comes in.

It works much like the virus itself, which uses RNA to program the cell to replicate it. In this case, RNA is used to reprogram the cell to remove what HIV has written into it.

Khalili and his team can put a 20-nucleotide strand of what's known as 'guide RNA' that basically goes into the cell, detects the HIV's genetic code, and cuts it out of the genome—making it as if the HIV had never existed. So far, the team has done it with t-cells and other human immune system cells that were cultured in the lab.

"We found that [the therapy] eradicates the HIV-1 genome and effectively immunizes target cells against HIV-1 reactivation and infection with high specificity and efficiency," Khalili wrote in Proceedings of the National Academy of Sciences, where his work was just published. "These properties may provide a viable path toward a permanent or 'sterile' HIV-1 cure, and perhaps provide a means to eradicate and vaccinate against other pathogenic viruses."

Obviously, this research is still in its infancy. It's one thing to delete HIV out of a few cells in a lab, another entirely to do it in a living, breathing human. But it's a hugely promising step that attacks HIV at its source. Any therapy that literally deletes HIV out of the genome would likely be more effective than other HIV treatments, because, even with antiretroviral drugs, a small "reservoir" of HIV remains in the body, which is liable to pop back up if a person ever stops treatment for any length of time.

Of course, there are plenty of problems that could pop up. It could be that the "guide RNA" ends up deleting genetic code beyond that contained in HIV, which could cause lots of problems or mutations. HIV is also highly variable—the virus mutates so often, which is one of the reasons why a vaccine has been so hard to develop. So, it might be that you'd need to create an individualized set of guide RNA for each patient, which would increase the difficulty of doing this on a widespread basis.

If those hurdles can be cleared, deleting HIV out of all of the infected cells in a body—perhaps in conjunction with some existing treatments—will, in theory, completely cure a person of the virus.

"We want to eradicate every single copy of HIV-1 from the patient. That will cure AIDS," Khalili said in a statement. "I think this technology is the way we can do it."

In any case, it's looking more and more like anything that is done to a genome can be undone. The genetic code we're born with, and the one we end up with through a series of mutations and viruses, might soon be edited at will.